Regulator for DC-DC power regulation, e.g., step-down regulator (converter) or buck regulator, can convert unregulated power of a DC (direct-current) power source to regulated voltage and current for a load, and is therefore essential for modern electronic, such as smart phone, mobile phone, tablet/notebook/portable computer, digital camera, digital camcorder, handheld game console, or wearable gadget (glasses, wrest ring, watch, armlet, earphone, headset), etc.